1. Field of the Invention
The present disclosure relates generally to electronic devices and, more specifically, to device having electronic memory.
2. Description of the Related Art
Low-power memory design has been a research area for many years, and power gating has become an industrialized technology used to place an array of memory cells into sleep mode or a shutdown mode. However, such techniques can be inefficient for managing power consumption, for example, when a small portion of a memory array needs to remain active the benefits of array level power gating can be largely negated.
In addition, static leakage power consumption of memory is becoming a significant portion of the total power used by memory, and, due to an exponential relationship of leakage current to voltage, lowering the voltage applied to a memory by a few hundred millivolts reduces the static leakage power consumption (and thus also the total power consumption) significantly. Such a lowered voltage level can be referred to as a drowsy voltage level, as power savings approaching those of a sleep mode can be realized by such a reduction of the voltage level from an operational voltage level to a drowsy voltage level. A memory can be said to be in a drowsy state when its voltage level is reduced to the drowsy voltage level, and can be understood to be a data retention state, as application of the drowsy voltage level to bit cells allows retention of data in such bit cells. However, a drowsy voltage level (e.g., a reduced voltage level) during an inactive state cannot be applied if there are weak bits in the memory array, which are bits of the array that are not able to maintain their storage state when a drowsy voltage level is applied. Such inability to maintain a storage state can be related to aging. When the bit array has a weak bit, then the bit array is prevented from being maintained in a low power state to save leakage power, as being in the low power state can alter the value stored in the weak bit. Thus, the presence of weak bits or even just the risk of occurrence of weak bits can impair the use of power saving techniques and effectively increase the power consumption of memory.
The use of the same reference symbols in different drawings indicates similar or identical items.